1 #define _DEFAULT_SOURCE
2 #include <string.h>
3
4 #define BITOP(a,b,op) \
5 ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
6
strcspn(const char * s,const char * c)7 size_t strcspn(const char *s, const char *c)
8 {
9 const char *a = s;
10 size_t byteset[32/sizeof(size_t)];
11
12 if (!c[0] || !c[1]) return strchrnul(s, *c)-a;
13
14 memset(byteset, 0, sizeof byteset);
15 for (; *c && BITOP(byteset, *(unsigned char *)c, |=); c++);
16 for (; *s && !BITOP(byteset, *(unsigned char *)s, &); s++);
17 return s-a;
18 }
19